Resonance mode analysis of DNA self-assembled metamolecules with an effective refractive index model

We investigated the feasibility of a simple effective refractive index model based on the finite-difference time-domain method for DNA self-assembled metamolecules. Metamolecules were fabricated with Au nanoparticles (AuNPs) and a two-layer rectangular DNA template. Simulated scattering spectra for AuNPs placed on the template (n_eff= 1.3), self-assembled DNA dimers (n_eff= 1.34), and quadrumers (n_eff= 1.5) matched well with experimental results. Dipolar and Fano-like resonances were predicted from the calculated field distribution. These results indicate that we can easily estimate the resonance mode of fabricated metamolecules on a glass substrate, even when they are surrounded by complex materials such as DNA, by using a simple refractive index model.